gomaxprocs.go

     1  // Copyright 2023 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // Tests increasing and decreasing GOMAXPROCS to try and
     6  // catch issues with stale proc state.
     7  
     8  //go:build ignore
     9  
    10  package main
    11  
    12  import (
    13  	"log"
    14  	"os"
    15  	"runtime"
    16  	"runtime/trace"
    17  	"time"
    18  )
    19  
    20  func main() {
    21  	// Start a goroutine that calls runtime.GC to try and
    22  	// introduce some interesting events in between the
    23  	// GOMAXPROCS calls.
    24  	go func() {
    25  		for {
    26  			runtime.GC()
    27  			time.Sleep(1 * time.Millisecond)
    28  		}
    29  	}()
    30  
    31  	// Start tracing.
    32  	if err := trace.Start(os.Stdout); err != nil {
    33  		log.Fatalf("failed to start tracing: %v", err)
    34  	}
    35  	// Run GOMAXPROCS a bunch of times, up and down.
    36  	for i := 1; i <= 16; i *= 2 {
    37  		runtime.GOMAXPROCS(i)
    38  		time.Sleep(1 * time.Millisecond)
    39  	}
    40  	for i := 16; i >= 1; i /= 2 {
    41  		runtime.GOMAXPROCS(i)
    42  		time.Sleep(1 * time.Millisecond)
    43  	}
    44  	// Stop tracing.
    45  	trace.Stop()
    46  }
    47
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